A point is a good starting reference in the physical world, and among
devices that respect absolute physical units. Printers worth their salt
know what a point is, but the display systems attached to 95+% of desktop
machines don't know a point from a pixel from a bit of sneeze-dew. Mac
users are generally out of luck unless they set their displays *physically*
to 72 dpi, as are most Windows folk unless their displays are 96 or 120 dpi
(hold a ruler up and count the dots...). I understand that some display
systems permit sophisticated users to map points to pixels however they
please. This will make points a good general unit as soon as 90% of users
have such a mapping as part of their personal profile, something that kicks
in when you enter a username and (network) password. Without rebooting -
perhaps even with a live point-to-pixel slider.... Let's say Windows 2002
is released in 2005, and reaches 90% penetration by 2009?
IIRC, when you set up XFree86 (the version of X11 commonly used on
free OSes such as GNU/Linux, FreeBSD, etc), you tell it the physical
size of your monitor. And an X11 call can be used to retrive this info.
(It's also been rumored that suns running X11 often return
incorrect information about the physical size of the screen.)
Having a points to pixels mapping *per user* would be stupid; I've
used several different telnet programs, X servers, etc. It might
be useful, though, for a user to ask for everything to be multiplied by
some factor, to accomodate near-blindness, etc.